Hispanic Americans in general and Hispanic youth in particular, carry a disproportionate share of the burden of substance use in the United States. Hispanic youth are also less likely than are Caucasian youth to benefit from treatment for alcohol and other drug (AOD) use. It remains unknown why this disparity persists after treatment. Two potential factors in this disparity are therapist behaviors and communication patterns during treatment sessions for AOD use. Previous research in adults has demonstrated a causal chain between therapist behavior, client behavior, and AOD outcomes. If therapists behave differently with Hispanic and Caucasian youth, then supervisors, trainers, and educators would have concrete behavioral targets to measure and change therapist behavior to improve these disparate outcomes for Hispanic youth. The proposed secondary analysis relies upon Eco developmental theory (Szapocznik & Coatsworth, 1999) to make specific predictions about within-session behaviors and processes. This study will use an advanced psychotherapy process research technique, sequential coding, to measure within-session behaviors of therapists and clients to test these hypotheses about how communication patterns and therapist behaviors may vary between Hispanic and Caucasian youth in an existing sample of 506 recorded psychotherapy sessions with adjudicated youth, and to link these behaviors to AOD outcomes. Using this large, existing sample of audio recordings from Project AMICA, a large randomized controlled trial to assess health disparities, complete with demographics, psychosocial assessments, and outcome data, will provide an unusual opportunity for a large, low-cost and high-impact study to examine health disparities effects. Evaluating client and therapist language in this study presents a unique opportunity to measure communication patterns from a randomized controlled trial of motivational interviewing with justice- involved youth. The proposed 4-year analysis of existing recordings will test a causal chain developed in adult populations, using an adolescent sample and comparing those effects for Hispanic and Caucasian youth, an approach that will guide clinical practice by either corroborating or challenging current approaches to psychotherapy for AOD use with Hispanic youth.